Instructions
Press the "L2" button to draw your weapon. This will create an aim box. If you are playing the Xbox 360 version of the game, you must press the "Left Trigger" button. If you are playing the PC version, press the right mouse button.
Press down on the left control stick to zoom in. This will shrink the aim box, allowing for more accurate aiming. If you are playing the PC version, scroll up on your mouse wheel while aiming to zoom in.
Press the "L2" button to fire your weapon. If you are playing the Xbox 360 version, press the "Left Trigger" button. If you are playing the PC version, press the right mouse button.